The data only shows how many currently licenced/taxed. Could a few more off road/sitting in a glass case etc.
Apparently it includes SORN bikes, so if a bike has been road-registered and then ends up in a glass case, in theory it should still be on the database.
For the 600 SS, I'm sure there are more than 9 licenced and 4 on SORN
I'd rather die peacefully in my sleep like my Grandfather, than screaming in terror like his passengers.- Jim Harkins